1. Field of the Invention
The present invention relates to an exposure apparatus, and more particularly to a scanning projection exposure apparatus which performs exposure while moving a first object and a second object.
2. Related Background Art
Liquid crystal display panels are frequently used these days as a display device for word processors, personal computers, televisions, etc. A liquid crystal display panel is fabricated by patterning of transparent thin-film electrodes in a desired shape on a glass substrate by the photolithography technique. As an apparatus for the lithography a mirror projection type aligner is used for exposure-printing an original pattern formed on a mask onto a photoresist layer on a glass substrate through a projection optical system.
FIG. 1 and FIG. 2 are drawings to show the structure of a conventional mirror projection type aligner. FIG. 1 is a perspective view to show the overall structure of the aligner and FIG. 2 is a lens cross-sectional view to show the structure of a projection optical system in the aligner.
In FIG. 1, an illumination optical system not shown illuminates a mask 71c in an arcuate illumination field 72a. An optical path of light from the illumination field 72a is deflected 90xc2x0 by a first reflecting surface 73a of a trapezoid mirror 73, as shown in FIG. 2, and the thus deflected light advances via a concave mirror 74 and a convex mirror 75 and then is reflected again by the concave mirror 74. The optical path of the light reflected by the concave mirror 74 is deflected 90xc2x0 by a second reflecting surface 73b of the trapezoid mirror. Then an image of the mask 71c or an image 72b of the illumination field 72a is formed on a plate 76.
The aligner as shown performs the so-called scanning exposure while moving the plate 76 and the mask 71c in the X direction in the drawings, whereby a circuit pattern on the mask 71c is transferred onto a selected region on the plate 76.
There is a recent demand to increase the size of liquid crystal display panels with such a demand to increase the size, the above-described aligner is also desired to enlarge the exposure area.
In order to meet the demand to enlarge the exposure area, the conventional exposure apparatus as described above employed a method of exposure with exposure area as divided into pieces. Specifically, as shown in FIG. 1, an exposure area on the plate 76 is divided into four regions of 76a to 76d, and with scanning exposure of mask 71a and region 76a a circuit pattern of mask 71a is transferred onto the region 76a. In the next place, the mask 71a is exchanged for another mask 71b and the plate 76 is moved stepwise in the XY plane in FIG. 1 before a region 76b comes to coincide with the exposure area of the projection optical system. With scanning exposure of mask 71b and region 76b, a circuit pattern of mask 71b is then transferred onto the region 76b. After that, the same step is repeated for masks 71c and 71d and regions 76c and 76d, whereby circuit patterns of masks 71c and 71d are transferred onto corresponding regions 76c and 76d. 
In such exposure with divided exposure area, the multiple scanning exposure steps must be taken for a single exposure area, which decreases the throughput (an exposed substrate amount per unit time). Further, in case of the partition exposure, there are seams or stitches between two adjacent exposure regions and, therefore, the stitching accuracy must be enhanced. Because of this requirement, the method had such disadvantages that the magnification error of projection optical system must be decreased as close to 0 as possible, that the alignment accuracy must be greatly improved, and that the production cost of the apparatus is increased.
On the other hand, it can be conceivable that the scale of projection optical system is increased for full scanning exposure of a single large exposure area instead of the partition exposure. In order to increase the scale of projection optical system, however, large-scale optical elements must be produced with very high accuracy, which results in increasing the production cost and the size of apparatus. Also, there was a disadvantage that the size increase of projection optical system caused an increase in aberrations or a decrease in imaging performance.
The present invention has been accomplished taking the above problems into consideration and an object of the present invention is to provide an exposure apparatus which can realize full scanning exposure of a large exposure area with excellent imaging performance and without lowering the throughput.
The above object and other objects will be further apparent form the following description.
Provided according to the present invention is an exposure apparatus for, while moving a first object and a second object in a certain moving direction, effecting projection exposure of an image of said first object onto said second object, comprising a first projection optical system for forming a real-size erect image of said first object on said second object, which is telecentric at least on an image side, a second projection optical system for forming a real-size erect image of said first object on said second object, which is telecentric at least on the image side and which is disposed next to said first projection optical system, a first field stop for limiting an exposure region to be formed on said second object by said first projection optical system, within a certain shape, and a second field stop for limiting an exposure region to be formed on said second object by said second projection optical system, within a certain shape, wherein a sum of a length along said moving direction, of the first exposure region limited by said first field stop and a length along said moving direction, of the second exposure region limited by said second field stop is constant over a direction perpendicular to said moving direction.
In the present invention, a scanning exposure apparatus performs such projection exposure that a real-size erect image (which is an image with positive horizontal and vertical lateral magnifications) of a circuit pattern formed on a mask as a first object is transferred through a plurality of projection optical systems onto a plate as a second object. A plurality of exposure regions formed on the plate through the respective projection optical systems are so arranged that a sum of lengths along the scanning direction is constant over the direction perpendicular to the scanning direction, that is, that an amount of exposure light becomes constant over the entire surface of plate.
Since the plurality of projection optical systems are so arranged that the sum of widths of exposure regions along the scanning direction is constant over the direction perpendicular to the scanning direction, single scan exposure can achieve a large exposure area on the whole even with compact projection optical systems and small exposure regions formed thereby.
Also, since each projection optical system is compact, scanning exposure can be made while minimizing occurrence of aberrations and keeping excellent imaging performance.
In case that each projection optical system is composed of two partial optical systems and that each exposure region formed on the plate is defined by the shape of an aperture in a field stop located at a position where an intermediate image of mask pattern is formed through a first partial optical system, a preferable arrangement is such that edges of the aperture are triangular and overlap with triangular edges of adjacent apertures in the scanning direction.
In case that the partial optical systems are Dyson optical systems, the center portion of each aperture excluding the both edges thereof is preferably defined by two straight lines. In case that the partial optical systems are Offner optical systems, the center portion is preferably defined by two arcs or by two polygonal lines.
It is further object of the present invention to provide an exposure apparatus for, while moving a first object and a second object in a certain moving direction, effecting projection exposure of an image of the first object onto the second object, comprising:
a first projection optical system for forming a real-size erect image of the first object on the second object, which is both-side telecentric; and
a second projection optical system for forming a real-size erect image of the first object on the second object, which is both-side telecentric and which is disposed next to the first projection optical system;
wherein each of the first and second projection optical systems has a refractive optical system of a positive refractive power and a plane reflective surface for reflecting light from the refractive optical system back to the refractive optical system.
It is further object of the present invention to provide an exposure apparatus for, while moving a first object and a second object in a certain moving direction, effecting projection exposure of an image of the first object onto the second object, comprising:
a first projection optical system for forming an erect image of the first object on the second object; and
a second projection optical system for forming an erect image of the first object on the second object, which is disposed next to the first projection optical system;
wherein each of the first and second projection optical systems has:
a first image-forming optical system arranged so that one of two conjugate points is located on the first object; and
a second image-forming optical system arranged so that one of two conjugate points is coincident with the other conjugate point of the first image-forming optical system and so that the other of the two conjugate points is located on the second object;
wherein either one of the first image-forming optical system and second image-forming optical system is an Offner optical system having a concave reflective mirror and a convex reflective mirror and arranged to guide light from one conjugate point to the other conjugate point while reflecting the light by the concave reflective mirror, the convex reflective mirror, and the concave reflective mirror in the named order; and
wherein the other of the first and second image-forming optical systems is a Dyson optical system having first and second reflective prisms, a lens group of a positive refractive power, and a concave reflective mirror with a concave surface to the lens group and arranged to guide light from one conjugate point to the other conjugate point via the first reflective prism, the lens group, the concave reflective mirror, the lens group, and the second reflective prism in the named order.
It is further object of the present invention to provide a projection optical system for forming an image of a first object on a second object, a projection optical apparatus comprising:
an optical system having an optical axis and at least one reflective surface coaxial with the optical axis;
first light splitting means disposed in an optical path between the optical system and the first object; and
second light splitting means disposed in an optical path between the optical system and the second object;
wherein a light beam passing the second light splitting means is transferred along a direction traversing the optical axis to be guided to the first light splitting means.
It is further object of the present invention to provide an exposure apparatus for, while moving a first object and a second object in a certain moving direction, effecting projection exposure of an image of the first object onto the second object, comprising:
a first reflective surface for deflecting light coming from the first object;
an image-forming optical system for forming an intermediate image of the first object, based on light coming from the first reflective surface;
a beam transferring member for transferring the light of from the first reflective surface and then through the image-forming optical system, along a direction traversing an optical axis of the image-forming optical system to guide the thus transferred light again to the image-forming optical system; and
a second reflective surface for deflecting the light of from the beam transferring member and then through the image-forming optical system, to the second object.
It is further object of the present invention to provide an exposure apparatus for, while moving a first object and a second object in a certain moving direction, effecting projection exposure of an image of the first object onto the second object, comprising:
a first projection optical system for forming an erect image of the first object on the second object; and
a second projection optical system for forming an erect image of the first object on the second object, which is disposed next to the first projection optical system;
wherein each of the first and second projection optical systems comprises:
a first reflective surface for deflecting light from the first object;
an image-forming optical system having an optical axis and two conjugate points, the image-forming optical system being disposed so that the first reflective surface is positioned on a side of one conjugate point out of the two conjugate points, and the image-forming optical system being for forming an intermediate image of the first object, based on light coming from the first reflective surface;
a beam transferring member for transferring the light of from the first reflective surface and then through the image-forming optical system, along a direction traversing the optical axis of the image-forming optical system to guide the thus transferred light again to the image-forming optical system; and
a second reflective surface for deflecting the light of from the beam transferring member and then through the image-forming optical system, to the second object.
It is further object of the present invention to provide a projection optical apparatus comprising:
an image-forming optical system having an optical axis and two conjugate points;
a field splitting member disposed on a side of one conjugate point of the projection optical system, for splitting a field of the projection optical system; and
a beam transferring member disposed on a side of the other conjugate point of the projection optical system, for transferring light passing via the field splitting member and the projection optical system in the named order, along a direction traversing the optical axis of the projection optical system.
It is further object of the present invention to provide an exposure apparatus for, while moving a first object and a second object in a certain moving direction, illuminating the first object by an illumination optical system and effecting projection exposure of an image of the first object onto the second object by a projection optical system a position of which is fixed relative to the illumination optical system:
wherein the illumination optical system comprises:
a first illumination optical system for forming a first illumination region on the first object; and
a second illumination optical system for forming a second illumination region different from the first illumination region on the first object;
wherein the projection optical system comprises:
a first projection optical system for forming an erect image of the first object illuminated by the first illumination optical system on the second object; and
a second projection optical system for forming an erect image of the first object illuminated by the second illumination optical system on the second object;
wherein the first illumination optical system comprises first illumination region moving means for moving the first illumination region on the first object relative to the first projection optical system; and
wherein the second illumination optical system comprises second illumination region moving means for moving the second illumination region on the first object relative to the second projection optical system.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.